Linear drive metal forming machine

ABSTRACT

The invention relates to a method and apparatus for forming metal containers. The method involves introducing a knockout element ( 110 ) into the container body through the open end, providing a forming die shaped to reduce the diameter of the sidewall of the container body ( 100 ) when the open end of the container body ( 106 ) is forced therein to produce a neck portion of reduced diameter on the container body, driving the open end of the container body into the forming die ( 108 ), retracting the knockout element through the neck portion as the neck portion is formed, and removing the container body ( 106 ) from the forming die ( 108 ) and knockout element ( 110 ). In the invention, the driving of the open end of the con tai ner body into the forming die and/or the movements of the knockout element are carried out under computer numerical control, preferably employing linear motor drives, thereby enabling the driving or movement to be optimized for the container body and the neck portion formed thereon.

TECHNICAL FIELD

The present invention generally pertains to the method and apparatus forproducing containers and, more particularly, to die necking of suchcontainers.

BACKGROUND ART

The technology for reducing the open-end portion of a closed endcontainer (necking) has been in existence for over one hundred years.The procedure was originally developed for artillery shells, with alarger diameter shell casing being reduced to retain a smaller diameterprojectile. The process by which this is accomplished today is calleddie necking. The basic concept of necking is to force a typicallycylindrical, thin walled metal body or shell at a given diameter andphysically push it into a die or series of progressively smaller dies.In this process a reduction in diameter of the open end is realized.

In metal food and beverage cans, the primary purpose for a reduceddiameter at the open-end is material savings, and thus realized as costsavings. Because the end panel is of a thickness that is on the order ofat least twice the thickness of a typical sidewall, as the diameter ofthe container is reduced, the amount of material necessary for the endpanel is reduced by a greater amount. In certain applications such asaerosol containers, the necking operation is performed to bring theopening to a specific diameter to facilitate a standard size valveassembly and eliminate any secondary adaptor that would otherwise benecessary. A secondary consideration of reducing the diameter of the endof the container is the reduction in the longitudinal stress exerted onthe end of the container. As the cap size is reduced, this stress isreduced and the thickness requirement of the end cap is also reduced.The third consideration for diameter reduction is visual. Manyaesthetically pleasing shapes can be achieved by necking conventionalcylindrical block shapes into tapered geometries and containers thatresemble bottles.

There are practical limits on the reduction of the diameter of thematerial for any given material in any given die. The strength of thecan body depends on a number of factors including the Young's modulusand yield stress of the material, the plate thickness and the candiameter. If the practical limit on diameter reduction is exceeded, thematerial will wrinkle, pleat, pucker or tear at a point inherent to thegeometrical characteristics and type of metal being necked.

Conventional die necking of metal containers is accomplished withlarge-scale machinery that is very difficult to develop the fine tunedproperties required to manufacture containers with significant necklength. The development of necking profiles is currently a long,involved, trial and error process that can take months to establish theproper parameters for each necking stage necessary to produce longneckcontainers. Specifically, current die necker technology uses hard camsto provide motion to pusher and knock-out rams. Key parameters such ascam profile and cam throw must be tested and tweaked with eachincremental change in the necking profile. Each time a change is made,the machine must be taken down and modified in a lengthy process toredesign and refit the new cams.

U.S. Pat. No. 5,355,710 discloses a conventional method and apparatusfor necking a metal container. The disclosure of this patent isspecifically incorporated herein by reference.

DISCLOSURE OF THE INVENTION

The present invention overcomes the disadvantages and limitations of theprior art by providing apparatus and methods for forming metalcontainers using computer numerical control.

By the term “computer numerical control” as used herein, we mean that acomputational device, such as a computer, is used to control the actionof a knockout ram and/or a pusher ram in a container die neckingapparatus and method.

In its simplest form, the motions of the pusher and the knockout ramsare preferably controlled by a prime mover such as a motor, powertransmission system, hydraulic system, etc., whose motion is controlledby a computer control system optionally via a displacement feedbackloop. In such a case, the computer numerical control systems checks theprescribed path that the user enters in for each ram to the displacementfeedback loop and makes adjustments to the prime mover accordingly. Thesystem preferably uses time as its base.

By the term “linear reciprocal prime movers” as used herein we mean amotor or other device that acts in a linear manner to apply force ormovement in a desired linear direction without relying on rotary hardcams or the like to advance a knockout element, a container body or adie. Examples of such prime movers include linear drive motors,hydraulic motors, pneumatic motors, or the like. Generally, such primemovers are characterized by greater ranges of linear movement than canbe obtained with traditional hard cams. The movement is reciprocal (i.e.can be produced in either direction) and generally highly controllable,despite the application of considerable forces. The most preferred primemovers for use in the present invention are linear drive electricmotors.

According to one form of the present invention, there is provided amethod of reducing the diameter of a sidewall of a seamless unitarymetal container body having a sidewall, an endwall at one end of thesidewall, an open end at an opposite end of the sidewall, and alongitudinal axis extending between the endwall and the open end. Themethod involves introducing a knockout element into the container bodythrough the open end, providing a forming die shaped to reduce thediameter of the sidewall of the container body when the open end of thecontainer body is forced therein to produce a neck portion of reduceddiameter on the container body, driving the open end of the containerbody into the forming die, retracting the knockout element through theneck portion as the neck portion is formed, and removing the containerbody from the forming die and knockout element. The method utilizes atleast one linear reciprocal prime mover arranged to create movement orforce in the direction of the longitudinal axis of the container body tomove the knockout element, or to force the container body into theforming die, or both.

According to another form of the present invention, there is provided anapparatus for reducing the diameter of a sidewall of a seamless unitarymetal container body having a sidewall, an endwall at one end of thesidewall, an open end at an opposite end of the sidewall, and alongitudinal axis extending between the endwall and the open end. Theapparatus comprises a knockout element adapted to be inserted into thecontainer body through the open end, a forming die shaped to reduce thediameter of the sidewall of the container body when the open end of thecontainer body is forced therein to produce a neck portion of reduceddiameter on the container body, means for driving the open end of thecontainer body into the forming die, means for retracting the knockoutelement through the neck portion as the neck portion is formed, andmeans for removing the container body from the forming die and knockoutelement. At least one of the means for driving the open end of thecontainer body into the forming die and the means for retracting theknockout element through the neck portion is a linear reciprocal primemover arranged to create movement or force in the direction of thelongitudinal axis of the container body to move the knockout element, orto force the container body into the forming die, or both.

The use of linear prime movers under computer numerical control formanipulating thin gauge metal offers a wide variety of advantages overconventional technology and is not limited to die necking. The presentinvention provides a high degree of versatility in forming operationsand a capability to change profile shaping and a variety of operatingparameters in real time. Cam development can be accomplished using thereadily adjustable process of the present invention to derive empiricaldata quickly and efficiently with programmable adjustment of variablessuch as motion, force and velocity. Stroke length can be adjusted bysimply dialing in the desired length on the fly and without shuttingdown operations as opposed to tearing the machine down, removing the camthat determines thrust, retooling the cam, replacing and testing the newstroke to determine if it matches the intended modification and finallyto determine if the modification matches the intended result on the camprofile. A variety of forming variables and associated ratios can becustomized and easily adjusted for individual operations and can becontrolled independently for each stage in a multiple stage machine. Thepresent invention allows forming operations that require a high degreeof variability and precision to be possible. It also allows machinery tobe developed which may have been impractical from a developmentstandpoint using current technology.

In a particularly preferred form, the present invention may thereforecomprise a method of reducing the diameter of the sidewall at the openend of a seamless unitary metal container body having a sidewalldisposed about a longitudinal axis and a unitary endwall at onelongitudinal end of the sidewall opposite to the open end comprising:placing the container body with the endwall in communication with adrive segment and the sidewall in communication with a forming segmenthaving a fixed position forming die of curvilinear configuration inlongitudinal cross section and located to form a juncture with theoriginal diameter of the sidewall and progressing with further reductionin diameter toward the open end of the container body; driving aknockout ram with a first linear drive motor that produces a reciprocalmotion in the longitudinal axis relative to the container; drawing aknockout that is connected to the knockout ram, the knockout disposed toengage an interior surface of the open end of the container and having asubstantially uniform reduced diameter corresponding to the reduction indiameter at the curvilinear configuration of the forming die; extendingthe knockout longitudinally with the first linear motor to a depthwithin the open end of the container body beyond the juncture with theoriginal diameter of the sidewall; driving a pusher ram with a secondlinear drive motor producing a reciprocal motion in the longitudinalaxis relative to the container; engaging an exterior surface of theendwall of the container with a pusher pad that is driven by the pusherram; transmitting a linear force by the second linear motor through thepusher ram to the pusher pad to the endwall of the metal container tothe sidewall of the metal container thus forcing the sidewall into thecurvilinear portion of the forming die; retracting the knockout whilethe linear force is being applied to the metal container during the dieforming process; reducing the diameter of the sidewall that iscontiguous to the open end of the unitary can body as the containerreaches an endpoint of the curvilinear configuration within the formingdie.

In another particularly preferred form, the present invention may alsocomprise an apparatus for reducing the diameter of a sidewall at theopen end of a seamless unitary container body, the sidewall disposedabout a longitudinal axis and a unitary endwall at one longitudinal endof the sidewall opposite to the open end comprising: a fixed positionforming die of curvilinear configuration in longitudinal cross sectionand located to form a juncture with the diameter of the sidewall andprogressing with further reduction in diameter toward the open end ofthe container body; a first linear drive motor producing a reciprocalmotion in the longitudinal axis relative to the container; a knockoutof-substantially uniform reduced diameter corresponding to the reductionin diameter at the curvilinear configuration of the forming die, theknockout extending longitudinally from a position outside of the openend of the container to a depth within the container body beyond thejuncture with the diameter of the sidewall; a second linear drive motorproducing a reciprocal motion in the longitudinal axis relative to thecontainer; a pusher ram connected to a pusher pad which engages theexterior surface of the endwall of the container, the second lineardrive motor which transmits a linear force through the pusher ram to thepusher pad to the endwall of the metal container to the sidewall of themetal container thus forcing the sidewall into the curvilinear portionof the forming die, the first linear drive motor able to retract theknockout while the linear force is being applied to the metal containerby the second linear drive motor during the die forming process.

In yet another particularly preferred form, the present invention mayalso comprise an apparatus for the development of metal containermanufacturing equipment comprising: an apparatus for reducing thediameter of a sidewall at the open end of a seamless unitary containerbody, the sidewall disposed about a longitudinal axis and a unitaryendwall at one longitudinal end of the sidewall opposite to the open endcomprising; a fixed position forming die of curvilinear configuration inlongitudinal cross section and located to form a juncture with thediameter of the sidewall and progressing with further reduction indiameter toward the open end of the container body; a first linear drivemotor producing a reciprocal motion in the longitudinal axis relative tothe container; a knockout of substantially uniform reduced diametercorresponding to the reduction in diameter at the curvilinearconfiguration of the forming die, the knockout extending longitudinallyfrom a position outside of the open end of the container to a depthwithin the container body beyond the juncture with the diameter of thesidewall; a second linear drive motor producing a reciprocal motion inthe longitudinal axis relative to the container; a pusher ram connectedto a pusher pad which engages the exterior surface of the endwall of thecontainer, the second linear drive motor which transmits a linear forcethrough the pusher ram to the pusher pad to the endwall of the metalcontainer to the sidewall of the metal container thus forcing thesidewall into the curvilinear portion of the forming die, the firstlinear drive motor able to retract the knockout while the linear forceis being applied to the metal container by the second linear drive motorduring the die forming process.

The present invention has numerous advantages over prior art. Theseinclude a high degree of versatility in forming operations and acapability to change operating parameters on the fly. Variables such asmotion, force and velocity are programmable and highly adjustable atanytime during the forming stroke. In combination with this variabilitythe present invention allows for alteration of the programming in realtime, and thus, modifications to the metal forming can be accomplishedrapidly and without shutting down or retooling the production equipment.This real time alteration of metal forming allows the apparatus to beutilized as a development tool to set manufacturing parameters onproduction machines that do not possess such variability.

The forming variables and associated ratios can be customized and easilyadjusted for individual operations and can be controlled independentlyfor each stage in a multiple stage machine. This can be accomplished onthe “push” side of the forming operation and also on the “pull side”with the same or different forces. These additional motions can be usedfor multiple necking stages or any other operation that require linearmotion such as expandable mandrels or for performance of otheroperations (i.e., bottom piercing etc.).

Numerous advantages and features of the present invention will becomereadily apparent from the following detailed description of theinvention and the embodiment thereof, from the claims and from theaccompanying drawings in which details of the invention are fully andcompletely disclosed as a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of the overallsystem of the present invention;

FIG. 2 is a schematic illustration of one embodiment of a die neckingoperation of a thin wall cylindrical beverage container;

FIG. 3 is a detailed schematic illustration of a die necking of thediameter of the sidewall of a seamless unitary metal container body;

FIG. 4 is a lateral view schematic illustration of one embodiment of adie necking operation of a thin wall cylindrical beverage container; and

FIG. 5 is an illustration similar to FIG. 1, but showing a computernumerical controller connected to the die necking apparatus.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 of the drawings discloses a schematic illustration of oneembodiment of the overall system and apparatus of the present invention.As shown in FIG. 1, the apparatus can be viewed as including a formingsegment 102 and a drive segment 104 (illustrated within dotted lines)that together carry out operations on a seamless unitary metal containerbody 106 to achieve a reduction in the diameter of the sidewall 106A ofthe body, an operation also known as die necking. Die necking isinitiated by the stroke of a first linear motor 116, which is preferablya linear drive motor, acting as a prime mover. The first linear motor116 generates an inwardly directed longitudinal force on a knockout ram114 that is transmitted to a knockout element 110 (often referred tosimply as a “knockout”). The knockout ram 114 is secured by a knockoutram bushing/die retainer 112 which allows the knockout ram to experiencelinear motion in the direction of the longitudinal axis 106B of themetal container 106. The ram bushing/die retainer 112 also holds andretains a forming die 108 through which the knockout ram 114 andknockout element 110 extend. A similar second linear motor 128 isprovided in the drive segment 104 and it generates an inwardly directedlinear force on a pusher ram 126 that extends through a pusher rambushing 124 to a pusher pad 122. The pusher ram bushing 124 secures thepusher ram 126 and allows the pusher ram to experience linear motion inthe direction of the longitudinal axis 106 B of the container body 106.The pusher pad consequently exerts force on a closed end wall 106C ofthe container body 106.

In order to initiate a die necking operation, the first linear motor 116is initiated to extend and insert the knockout element 110 inside theopen-ended metal container 106 beyond a point where a reduction in thediameter of the sidewall will occur. Once the knockout element 110 is inplace, the second linear motor 128 transmits a longitudinal forcethrough pusher ram 126 to pusher pad 122. The metal container body 106is consequently driven into and contacts a shaped inner forming surface108A of the forming die 108 from the receiver end. Air (or other gas)under pressure is introduced into the interior of the container bodythrough a channel 120 in knockout element 110 to pressurize thecontainer body 106 in order to maintain its structural integrity in theradial direction during the necking operation. Concurrently, sufficientlinear force is transmitted from the drive segment 104 to allow the openend 106D of the container body 106 to conform to the shape of the innersurface 108A of the forming die 108 to form a neck portion 106E whilethe first linear motor 116 retracts the knockout element 110 out of thecontainer body 106 through the neck portion 106E as it is formed inorder to maintain support on the inside diameter of the sidewall and toassist in drawing the metal in a longitudinal direction. As the pusherpad 122 reaches the maximum stroke, as determined by the second linearmotor 128, the complete withdrawal of the knockout element 110 and theair pressure within the container body 106 serve to release thecontainer body 106 from the forming segment 102 of the apparatus.

FIG. 2 of the drawings discloses a more detailed schematic illustrationof one embodiment of the die necking operation of the present invention.As shown in FIG. 2, the die necking (reduction of the diameter) of asidewall 206A of a seamless unitary metal container body 206 isinitiated by the stroke of a first linear motor 216. The first linearmotor 216 generates a longitudinal force that is transmitted to aknockout element 210. The knockout element 210 is extended and insertedinside the open-ended metal container body 206 beyond a point where areduction in the diameter of the sidewall will occur. Once the knockoutelement 210 is in place, a second linear motor 228 transmits alongitudinal force to a pusher pad 222.

An open end 206D of the metal container body 206 is driven into andcontacts the inner forming surface 208A of a forming die 208 from thereceiver end. Air under pressure is introduced into the interior of thecontainer body 206 through a channel 220 passing through the knockoutelement 210 and is utilized to pressurize the container body 206 tomaintain its structural integrity in the radial direction during thenecking operation. Concurrently, sufficient linear force is transmittedfrom the second linear motor 228 to allow the container body 206 toconform to the shape of the inner surface 208A of the forming die 208while the first linear motor 216 retracts the knockout 210 out of thecontainer body 206 to maintain support on the inside diameter of thesidewall in the neck portion 206E as it is formed, to assist in drawingthe metal in a longitudinal direction and to prevent pleating of themetal container 206 in the neck portion. After the pusher pad 222reaches the maximum stroke, as determined by the second linear motor228, the knockout element and the air pressure inside the container bodypush the can body from the forming die. This is possible as the pusherpad commences to move away from the forming die. The knockout element isreversed during this step in order to push the can from the die.

As detailed in FIGS. 1 and 2, these die necking processes reduce thecontainer diameter by a few millimeters in each operation. If a greaterreduction is attempted, the material undergoes a hoop buckling failureknown as “pleating.” The use of the knockout element helps to preventthis failure. The profiles of the forming die and the knockout elementmatch each other, so that the gap between them is about 1.03 to 1.5times the material thickness. This is sufficient to permit the materialto pass through with slight thickening, but will not permit the materialto pleat.

By using the type of apparatus disclosed herein, and exhibiting a greatamount of control on the speeds and forces necessary to produce thecontainer, the problem of pleating can be eliminated, and far greaterreductions in diameter are possible. The achievable reduction is stilllimited, however, by the force that can be applied to the metalcontainer.

FIG. 3 of the drawings discloses a more detailed schematic illustrationof one embodiment of the die necking operation on the sidewall of aseamless unitary metal container body. As shown in FIG. 3, a metalcontainer 306 with an initial container diameter 334 is pushed into aforming die 308 and applied force from a linear motor (not shown) istransmitted through the body of the container by the container side wall306A. With this application of linear force, the container sidewall 306Aconforms to the shape of the die forming surface 308A and is preventedfrom pleating by the knockout element 310. The container sidewall 306Ais shaped in the necked portion of the container 306E from an initialcontainer diameter 334 to a final container diameter 336. The maximumforce that can be applied to form the necked portion of the container306E is limited by the strength of the container body 306. If thenecking force exceeds the strength of the container body then thenecking will cease and the container will be crushed.

The present invention allows substantial variability not only on the“push” side of the forming operation but also on the “pull” side. Thepull side is driven by a linear motor that retracts or removes theknockout element 310 from the metal container 306 as the containersidewall 306A conforms to the die forming surface 308A. The pull of theknockout element 310 during the push phase of the forming operationassists in drawing the open end 306D of the container sidewall 306A intothe forming die 308 and in maintaining proper wall thickness and shapeover the necked portion of the container 306E. It is the force and thevelocity of the push and pull, as well as their ratios to one another,that determine the ability and precision with which the apparatus isable to shape the metal container body 306. These push/pull force orvelocity ratios and discrete values can be varied individually for eachnecking stage as well as through an individual forming stroke. Becausemetals can only be cold worked to a limited extent based on theirinherent physical properties, this process is usually performed as anumber of repeated die necking sequences. This produces a more smoothand tapered neck on the container. After undergoing an initial formingoperation in an original die, the metal container is subjected to aseries of additional forming operations (possibly as many as 50 or so)using dies with increasingly aggressive curves, each of the successivedie necking operations partially overlaps and reforms only a part of thepreviously formed portion to produce a smooth tapered neck of desiredlength. The necked portion may increase the fill capacity of thecontainer and may also contain walls which have been thickened in thenecking process, and therefore, provide greater crush strength in thenecked area independently of the profile.

FIG. 4 of the drawings discloses a detailed schematic illustration ofone embodiment of the die necking operation of the present invention. Asshown in the lateral view of FIG. 4, a star wheel assembly 400 isutilized to facilitate the automated insertion and extraction of metalcontainers 406 from the metal forming apparatus. Pre-necked containers406 are loaded into a chute 440 which is supported by the chute mount444. The containers are stacked and oriented side-to-side awaitinginsertion to the star wheel assembly 400 at a star wheel insertion point442. Upon each cycle of a linear motor 428 that produces a die neckingoperation on a metal container, the star wheel assembly indexes byrotating clockwise 45 degrees (in this particular embodiment). The dienecking operation as described in the previous drawings in performed ata star wheel necking point 446 where the metal container alignslongitudinally with the linear motors and forming die assembly (notshown) as previously described. After undergoing the die neckingoperation at star wheel necking point 446, the necked metal container isindexed within the star wheel assembly 400 and continues in a clockwisemanner to a point where it is removed from the star wheel assembly 400at a star wheel extraction point 448. The finished container 406′ iscollected in a pick up gutter 450 which is supported by a pick up guttermount 452.

By utilizing linear motors as in the above examples, advantages overconventional methods and devices are realized. The disclosed inventionallows the relative motion of the pusher and knockout element to becapable of a highly variable velocity (push/pull) ratio throughout theneck forming operation. In this manner the velocity ratio (push/pull)can be varied for the individual necking stages and through anindividual stroke. By including a microprocessor driven controller, theforces, velocities and respective ratios can all be independentlyprogrammable and highly adjustable at anytime during the forming stroke.

By using an apparatus as detailed in FIG. 1, four independent motionsrelative to a fixed die position are possible (two on the pusher sideand two on the knockout side). Forming operations can be performed onboth ends of the motors stroke or the same operation can be performed ateither end with the same or different forces. These additional motionscan be used for multiple necking stages or any other operation thatrequire linear motion such as expandable mandrels or for performance ofother operations (i.e., bottom piercing etc.). As with the primarycontainer forming motions, these additional motions are alsoprogrammable and highly adjustable at anytime during the forming stroke.

The forming forces described within the aforementioned examples are alsoprogrammable and highly adjustable anytime during the forming stroke.They can be customized and adjusted for individual operations andadjusted independently for each stage in a multiple stage machine.Connecting linear motors in tandem can also increase these forces tonearly any extent necessary.

Since the aforementioned method and apparatus have the advantage ofbeing highly versatile in forming operations, with parameters such asmotion, force and velocity capable of being changed on as an operationproceeds, the system is highly applicable in the area of containermanufacture development. Modifications to the metal forming can beaccomplished rapidly and without shutting down or retooling theproduction equipment. Container profiles can be developed quickly andeasily using these alterations and optimization features. This allowsthe invention to be utilized as a laboratory or development tool to setmanufacturing parameters on production machines containing lesssophistication, variability and cost for purposes of mass production.

The apparatus of the present invention is preferably controlled by acomputer control system, optionally by a displacement feedback loop. Thecomputer may be used to control the prime movers acting on the pusherand knockout rams, and optionally the supply of pressurized fluid to theinterior of the container body. Thus, the computer may be used tocontrol such variables as the stroke length of the knockout ram and/orthe pusher ram, the velocity ratios of the rams, the strip air timing,pressure and pressurization profile, and adjustments for different necklengths (e.g. by adjusting pin height). Such adjustments may be made bymodifications of a computer control program (computer numerical control)via a variety of available user interfaces.

A simplified example of such a system is illustrated in FIG. 5. Thisshows apparatus similar to that of FIG. 1, with the same referencenumerals used to indicate the same elements, except that the numeralsbegin with a “5” rather than “1”. FIG. 5 additionally shows a computercontroller 580 that may be accessed via a monitor and keyboardarrangement 582. The computer controller is connected via wires toactuators controlling the motors 528 and 516 and the air supply viachannel 520. The apparatus includes a displacement feedback loop (notshown), i.e. means for measuring the displacement (or othercharacteristics) of the knockout and pusher rams and for returning thisinformation to the computer controller 580 so that the information canbe compared with the instructions programmed into the controller. Thecomputer controller can therefore check the prescribed path that a userenters in for each ram to the displacement feedback loop and makesadjustment to the prime movers accordingly. The system preferably usestime as its base. Alternatively, the system may use a desired velocityratio (i.e. the ratio of the knockout velocity relative to the pushervelocity), which may be held constant or variable, and then the computercontroller may determine what path the knockout element or pusher shouldfollow to satisfy the velocity ratio.

A further alternative way of establishing differential motion betweenthe pusher and knockout (i.e. similar to the velocity ratio), which mayhelp to optimize the process, is to measure the pusher load or the loadthat the prime mover sees on the pusher side. The load is then used inthe feedback loop to control the acceleration, velocity, and/or thedisplacement ratios between the pusher and knockout rams so that themachine minimizes the load, thus minimizing the load placed on thecontainer being necked. It may be necessary to compensate for the loaddue to the air pressure that is used to strip the container body fromthe forming die in the apparatus. Just before the container is necked,the container is filled with air at pressure greater than atmosphericpressure. This compensation may be accomplished by using the load in thefeedback loop only during the neck forming periods of the machine cycleand/or by measuring the pressure load throughout the cycle andaccounting for it.

The feed back loop mentioned above may be used to minimize the load thatis applied to a container body during the necking operation. Thus, theretraction of the knockout element can be detected and controlled toreduce the force necessary to cause the necking as the container body isforced into the forming die. The knockout element helps to draw thecontainer body into the forming die as it shapes the necked portion,thus enabling the pushing force on the container body to be reduced. Thecomputer controller can be used to sense and control these respectiveforces to apply the minimum forces required to achieve proper necking.

Also adjustable is the “pin height”. This is the distance between thepusher pad and the shaping die and it can be adjusted using the computercontroller to control the prime movers using the displacement feedbackloops to provide the desired setting input by the user. A locking systemmay then be used to “fix” the adjustment to ensure that it does notchange during the course of operation. Thus container bodies ofdiffering size may be accommodated by equipment of one kind. A variationof this is to use the computer control system that adjusts the pinheight to also move during the necking process to provide velocityratios other than those inherently built into a hard cam system.

As far as controlling the air pressure to the container body during andafter necking is concerned, the computer controller may be used to slowdown the flow of air to the interior of the container body when acertain pressure has been reached. Air slowly leaks from the containeraround the knockout element so a continual flow or air into thecontainer body is required to compensate for this. However, if anexcessive flow of air is maintained after optimal pressure has beenreached, more air merely leaks around the knockout element and costs areincreased by the resulting air flow losses. By providing a pressuresensor in the container body, e.g. on the knockout element, the computercan be notified when the pressure has reached the optimum value and avalve may be adjusted by the computer controller to minimize the airflow necessary to maintain the desired pressure.

The way in which the air flow is controlled during the necking operationis referred to as strip air timing. As well as optimizing strip airtiming for a particular container body, the computer controller can beused to adjust the strip air timing when adjusting neck profiles inorder to provide the air flow at the right time. The pressure may alsobe optimized to allow for the buildup of air so that maximum pressure isreached when needed in order to reduce neck defects and provide theforce necessary to strip the container body from the forming die.

Ideally, therefore, the apparatus of the present invention hasinfinitely adjustable pusher and knockout ram motion, infinitelyadjustable velocity ratios, infinitely adjustable strip air timing,pressure and pressurization profiles, simple adjustments for differentneck lengths (by adjusting stroke and pin heights), with simpleadjustment for containers of different heights (by adjusting the pinheight). These adjustments are made to take effect via modifications ofthe computer control program and are made possible by using at least onelinear reciprocal and controllable prime mover.

Although the apparatus of the present invention preferably hasinfinitely adjustable prime movers in both the forming segment and thedrive segment, this is not essential. A conventional hard camarrangement may be provided in one of these segments with a reciprocalprime mover in the other. The term “hard cam” refers to a physical cam(hardware as opposed to software) of the conventional kind that, uponrotation, causes a longitudinal movement of the pusher ram or knockoutram. The hard cam may move the pusher or knockout ram that has a strokelength sufficient to be able to neck container bodies with neck lengths,container heights and diameters that would be within the expected range,while using a computer controlled reciprocal linear prime mover on theother ram.

Indeed, hard cams may be used to move both the pusher and the knockoutrams, providing stroke lengths sufficient to neck containers with necklengths, can heights and diameters that would be within an expectedrange. Then, a computer controlled reciprocal linear prime mover may beused to control the pin height between the pusher side relative to thedie/knockout side of the machine and to lock the distances in so thatthere would be no movement during necking. Alternatively, the separationbetween the two sides need not be locked relative to one another, usingthe computer controlled system to obtain the effect of differentvelocity ratios between the pusher and knockout rams.

As a further alternative, it is possible, instead of pushing thecontainer body into the shaping die, to hold the can stationary and topush the shaping die onto the container body to form a neck portion. Theuse of a knockout element is still be required in the same way. Themotions of the die and knockout rams may be coordinated for optimalresults. A linear prime mover is used to control the motion of theshaping die in such cases.

As a still further alternative, the invention may be used to form aflexible neck profile machine. Where one set of tooling is designed insuch a way that it may be used to neck containers with vastly differentneck profiles without the need of all new tooling. In this case, only afew new tools would be required most likely at the beginning and endingstages of the neck tooling progression.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications that are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

Although the following claims define particular combinations offeatures, it should be kept in mind that other combinations of suchfeatures are possible, and all such possible combinations of featuresform part of the present invention.

1. A method of reducing the diameter of a sidewall of a seamless unitarymetal container body having a sidewall, an endwall at one end of thesidewall, an open end at an opposite end of the sidewall, and alongitudinal axis extending between the endwall and the open end, whichmethod comprises: introducing a knockout element into the container bodythrough the open end, providing a forming die shaped to reduce thediameter of the sidewall of the container body when the open end of thecontainer body is forced therein to produce a neck portion of reduceddiameter on the container body, driving the open end of the containerbody into the forming die, retracting the knockout element through theneck portion as the neck portion is formed, and removing the containerbody from the forming die and knockout element; characterized in thatthe driving of the open end of the container body into the forming dieand/or the movements of the knockout element are carried out undercomputer numerical control, thereby enabling said driving or movement tobe optimized for said container body and said neck portion formedthereon.
 2. A method according to claim 1, characterized in that atleast one linear reciprocal prime mover arranged to create movement orforce in the direction of the longitudinal axis of the container body isused to move the knockout element, or to force the container body intothe forming die, or both.
 3. A method according to claim 2, wherein thelinear reciprocal prime mover comprises a linear motor drive.
 4. Amethod according to claim 2, characterized in that said at least onelinear reciprocal prime mover is adjustable with respect to the extentor pattern of movement of the knockout element or the forcing of thecontainer body into the forming die, or both, thereby enabling themethod to be carried out on container bodies of different kinds bysuitably adjusting said at least one reciprocal prime mover toaccommodate said different kinds of container bodies.
 5. A methodaccording to claim 1, characterized in that a single linear reciprocalprime mover under computer numerical control is provided to move theknockout element or to force the container body into the forming die,and a rotary hard cam device is used for the remaining function ofmoving the knockout element or forcing the container body into theforming die.
 6. A method according to claim 1, characterized in that twolinear reciprocal prime movers are provided, one to move the knockoutelement and a second to force the container body into the forming die.7. A method according to claim 1, characterized in that at least onerotary hard cam unit is provided to move the knockout element, or toforce the container body into the forming die, or both, and at least onelinear reciprocal prime mover under computer numerical control is usedto move said at least one rotary hard cam unit to pre-position saidrotary cam unit suitable for a necking operation.
 8. A method accordingto claim 1, characterized in that at least one rotary hard cam unit isprovided to move the knockout element, or to force the container bodyinto the forming die, or both, and at least one reciprocal prime moveris used to move said at least one rotary hard cam unit as said method ofreducing the diameter o the sidewall of the container body proceeds. 9.A method according to claim 1, characterized in that a fluid isintroduced under pressure into the container body as the neck portion isformed to provide rigidity to the container body and to assist withremoving of the container body from the forming die.
 10. A methodaccording to claim 9, characterized in that flow rate and pressure ofsaid fluid in the container body is provided under computer numericalcontrol as said method proceeds to minimize loss of fluid from thecontainer body.
 11. An apparatus for reducing the diameter of a sidewallof a seamless unitary metal container body having a sidewall, an endwallat one end of the sidewall, an open end at an opposite end of thesidewall, and a longitudinal axis extending between the endwall and theopen end, which apparatus comprises: a knockout element adapted to beinterested into the container body through the open end, a forming dieshaped to reduce the diameter of the sidewall of the container body whenthe open end of the container body is forced therein to produce a neckportion of reduced diameter on the container body, means for driving theopen end of the container body into the forming die, means for movingand retracting the knockout element through the neck portion as the neckportion is formed, and means for removing the container body from theforming die and knockout element; characterized in that at least one ofsaid means for driving the open end of the container body into theforming die and said means for moving the knockout element through theneck portion is under computer numerical control, thereby enabling saiddriving or movement to be optimized for said container body and saidneck portion formed thereon.
 12. An apparatus according to claim 11,characterized in that a linear reciprocal prime mover arranged to createmovement or force in the direction of the longitudinal axis of thecontainer body under said computer numerical control is provided to movethe knockout element, or to force the container body into the formingdie, or both.
 13. An apparatus according to claim 12, characterized inthat said at least one linear reciprocal prime mover is adjustable withrespect to the extent or pattern of reciprocation of the knockoutelement or the forcing of the container body into the forming die, orboth, thereby enabling the apparatus to be used with container bodies ofdifferent kinds by suitably adjusting said at least one reciprocal primemover to accommodate said different kinds of container bodies.
 14. Anapparatus according to claim 12, characterized in that said linearreciprocal prime mover comprises a linear motor drive under saidcomputer numerical control.
 15. An apparatus according to claim 12,characterized in that a single linear reciprocal prime mover is providedto move the knockout element or to force the container body into theforming die, and a rotary hard cam device is used for the remainingfunction of moving the knockout element or forcing the container bodyinto the forming die.
 16. An apparatus according to claim 12,characterized in that two linear reciprocal prime movers are provided,one to move the knockout element and a second to force the containerbody into the forming die.
 17. An apparatus according to claim 12,characterized in that at least one rotary hard cam unit is provided tomove the knockout element, or to force the container body into theforming die, or both, and at least one linear reciprocal prime mover isprovided to move said at least one rotary hard cam unit to pre-positionsaid rotary cam unit suitable for a necking operation.
 18. An apparatusfor claim 12, characterized in that at least one rotary hard cam unit isprovided to move the knockout element, or to force the container bodyinto the forming die, or both, and at least one reciprocal prime moveris provided to move said at least one rotary hard cam unit.
 19. Anapparatus according to claim 12, characterized in that said at least onereciprocal linear prime mover acts on said container body to force saidcontainer body into said forming die.
 20. An apparatus according toclaim 12, characterized in that said at least one reciprocal linearprime mover acts on said forming die to force said container body intosaid die.
 21. An apparatus according to claim 11, characterized in thata supply of fluid is provided to introduce fluid under pressure into thecontainer body as the neck portion is formed to provide rigidity to thecontainer body and to assist with removing of the container body fromthe forming die.
 22. An apparatus according to claim 21, characterizedin that a computer controller is provided to vary a flow rate andpressure of said fluid into the container body in order to minimize lossof fluid from the container body.
 23. An apparatus according to claim11, characterized in that said at least one linear reciprocal primemover is a linear electric motor, a hydraulic motor or a pneumaticmotor.